A. Field of the Invention
The increase use of electronic equipment and communications has stimulated the necessity for shielding enclosures utilized in anechoic chambers, communication facilities, test units, securement-of-conference rooms, portable communications, MRI, Tempest, Computer and HEMP facilities utilized by government agencies, private business sector and the medical field. Each enclosure requires an opening for exit and entrance, resulting in a need for a system to protect against emissions resulting from Radio Frequency Interference and Electromagnetic Interferences. The most vulnerable and used part is the door assembly, in that it is the most critical component of the shielding enclosure constantly ensuring attenuation. All shielded enclosures are required to meet Standards set forth in Shielding Effectiveness Specifications in regards to attenuated values of RFI/EMI Radiation emissions into or out of enclosure or system.
B. Description of the Prior Art.
A major problem facing the State-of-the-Art shielding enclosure door assemblies is their inability to meet the attenuated RFI/EMI emission values established within industry standard specifications and to provide continual performance levels without constant maintenance on fragile contact surfaces. Shielding enclosure door systems have numerous disadvantages such as; the hinderance of cumbersome heavy door leaf weights, dangerous automated door closure mechanical devices, lacks operational safety for quick egress, continual maintenance requirements for cleaning and replacement of contact interfaces such as pneumatic bladders and finger stock. For example; flexible conductive finger stock mounted into door casing, engages door leaf knife edge when in the closed mode, show extreme susceptibility to contaminants directly attributes to lower shielding effectiveness, thus high cleaning maintenance is required and the fragile finger stock is very susceptible to breakage resulting in replacement and significant shielding loss. Another magnetic seal application was the hybrid approach of combining permanent and electromagnets in attempt to increase magnetic field strength to seal door leaf to door casing assembly. Special difficulties are attributed to this type of system including but not limited to; control electronics, inadequate magnetic field strength, door leaf and casing contact surface/structure variables create structural misalignment and contact surface incongruities including such that any type of abrasion, nick or contaminants located in the contact seal area results in extreme shielding effectiveness loss and can result in total door replacement, electrical circuity for electromagnets are required to be enclosed within a sealed RF tight conduit and electronically filtered prior to entry into enclosure, the inability to control heat build-up within the door structure results in buckling of contact sheet preventing an efficacious seal, these and other characteristics lead to a system unable to meet reliability and industry shielding effectiveness performance standards. The use of permanent magnetic materials in the door assembly was an attempt to increase magnetic field strength and is essential to implement door opening, in both cases it is ineffective. This prior art application relies totally on the ability to provide an efficacious and gapless seal, with low electrical resistance at the contact interfaces, between door leaf and door casing, which is very difficult if not impossible to achieve on a continual basis, leaving this application impractical and ineffective in attenuating RFI/EMI emissions into or out of an enclosure.